Motor control centers (MCCs) are assemblies designed to contain motor starters, variable frequency drives, programmable controllers, meters and other industrial electrical equipment. MCCs are commonly used in manufacturing facilities, power plants and other industrial locations.
A typical MCC includes one or more cabinet-like enclosures, each including a plurality of compartments or “buckets” configured to receive motor controllers and/or other types of modules. MCCs typically include one or more power bus bars to which these modules are connected. For example, a module may include “stab” contacts that extend from a rear face of the module and that are configured to engage power bus bars located proximate a rear section of the bucket into which the module is placed. These contacts may be moveable and may be actuated to engage with and disengage from the power bus bars using a motor drive and/or a tool interface at a front face of the module. MCC and module configurations are described, for example, in U.S. Pat. No, 8,054,606 to Morris et al. and U.S. Patent Application Publication No. 2011/0149480 to Leeman et al.
Within a given MCC, certain loads may be more critical than others. For example, in a nuclear power plant, motor controllers that control motor operated valves (MOVs) that control flow of cooling water to the reactors may be more critical than other loads. Under emergency conditions, it is generally desirable to keep these critical loads on line. Accordingly, nuclear power plants typically have redundant power systems that are configured to power critical loads from a secondary power source, such as a permanently-installed backup diesel engine-generator set. Unfortunately, however, these secondary power systems may also fail, as was the case, for example, in the Fukushima Daiichi nuclear disaster of 2011.